Blood samples are critical to the detection, diagnosis and progression of diseases and the treatment of many diseases. Pathogens, toxins (e.g., those produced by pathogens) and bodily defense molecules (e.g., antibodies, cytokines, etc) can be detected and monitored for a variety of disease states and treatment progression by analysis of, for example, a subject's blood sample.
Such analyses may include, for example, immunological, genetic and pathogenic analyses. In underdeveloped areas of the world it is often necessary to obtain a blood sample from a subject and transport it to a distant laboratory facility for processing and analysis. In other instances, samples may be delayed or may need to be stored for extended periods of time prior to testing. In order to obtain accurate results the sample must be stably maintained until analysis. Further, complete or near complete recovery of the sample is often critical to ensure accurate results.
Dried blood spot (DBS) testing is a well-known methodology for collecting and stabilizing a blood sample for later analysis. In this method, a blood sample is absorbed into a substrate (commonly filter paper such as Whatman 903®), and dried. For example, in the prior art, the blood may be held within the fibers or on the substrate. Other fibrous materials may also be used as substrates for DBS testing such as cellulose acetate fibers, cellulose, nitrocellulose, carboxymethylcellulose, hydrophilic polymers, polypropylene, polyester, polyamide, carbohydrate polymers, polytetrafluroethylene, cotton, fiberglass and combinations thereof. See, U.S. Pat. No. 7,638,099 to Lloyd, et al. In each case, the substrate is inert so as not to interfere with the intended assay.
In order to analyze a dried blood spot, extraction or solubilization from the filter paper (or other substrate) is required. For that purpose the filter paper, or a portion (usually a disc), is cut out of the filter paper and is placed into a container. The extraction procedure is then carried out using an appropriate solvent. After extraction and centrifugation, the supernatant is collected and analyzed.
The conventional DBS method described briefly above, by its very nature, results in extended processing time because of the need to resolubilize the sample from the substrate. Further, loss of sample or sample components may occur because of retention on the filter paper. Further still, portions of the filter paper (e.g., paper punches) selected for resolubilization may not provide for an even representation of the distribution of sample across the filter paper. These problems with the present technology introduce significant variability and bias into assay results. U.S. Patent Application No. 2013/0090253 to Dixon, et al.
Prior art methods of correcting for these problems are either complicated or ineffective. U.S. Patent Application No. 2013/0090253 to Dixon, et al., proposed a method of excising a sector-shaped (wedge) sample from a DBS instead of a circular paper punch stating that the sector-shaped sample would provide for a more accurate sample distribution. However, this method does not solve the problem of sample retention.
U.S. Pat. No. 7,638,099 and U.S. Patent Application No. 2009/0246750, both to Lloyd, et al., are directed towards a complicated container for the collection and air-drying of bodily fluid samples, said device comprising a matrix made of absorbent materials such as cellulose acetate fibers, cotton, etc. The container of Lloyd, et al., is expensive to manufacture and does not solve the problems recognized herein with regard to sample retention.
U.S. Patent Application No. 2004/0132207 to Arima, et al., discloses a method of stabilizing a blood sample by collecting it in pH buffered reagents and storing the sample in a buffer with a mildly weak acidic pH in the range of pH 7.0 to 8.0. The method requires fluid reagents, dedicated collection devices and does not provide for dry storage and transport of a blood sample.
U.S. Patent Application No. 2006/0057554 to Watling, et al., discloses a sample collection device for a fluid sample comprising an inert (non-dissolvable) absorbing matrix. Watling discloses that the absorbent material may be in the shape and size of a small tablet and, thus, frequently refers to the inert absorbing matrix as a tablet. See, Watling ¶¶ [0017], [0023] and [0029]. However, since the matrix of Watling is inert and non-dissolvable Watling does not solve the retention problems of the prior art.
U.S. Patent Application No. 2013/0280725 to Ismagilov, et al., discloses a complicated microfluidic device for preservation and storage of fluid biospecimens, the device comprising a membrane and/or desiccant.
What is needed are new materials and methods that provide for the increased efficiency and accuracy of blood sample acquisition and processing in a cost effective manner.